[clientgen] Consider using <depends>/<produces> so that wsimport won't do unnecessary compilation
[clientgen] parsing WSDL...
[clientgen]
[clientgen]
[clientgen] [WARNING] src-resolve: Cannot resolve the name 'xsdLocal1:ListOfCustomObject13' to a(n) 'element declaration' component.
[clientgen] line 1 of file:/C:/temp/CustomObject13.wsdl#types?schema2
[clientgen]
[clientgen] [WARNING] src-resolve: Cannot resolve the name 'xsdLocal2:ListOfCustomObject13' to a(n) 'element declaration' component.
[clientgen] line 1 of file:/C:/temp/CustomObject13.wsdl#types?schema2
[clientgen]
[clientgen] [ERROR] Two declarations cause a collision in the ObjectFactory class.
[clientgen] line 1 of file:/C:/temp/CustomObject13.wsdl
[clientgen]
[clientgen] [ERROR] (Related to above error) This is the other declaration.
[clientgen] line 1 of file:/C:/temp/CustomObject13.wsdl
[clientgen]

BUILD FAILED
weblogic.wsee.tools.WsBuildException: Error running JAX-WS clientgen: null
at weblogic.wsee.tools.clientgen.jaxws.ClientGenImpl.execute(ClientGenImpl.java:175)
at weblogic.wsee.tools.anttasks.ClientGenFacadeTask.execute(ClientGenFacadeTask.java:251)
at weblogic.wsee.tools.anttasks.ClientGenTask.execute(ClientGenTask.java:365)
at org.apache.tools.ant.UnknownElement.execute(UnknownElement.java:288)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.tools.ant.dispatch.DispatchUtils.execute(DispatchUtils.java:106)
at org.apache.tools.ant.Task.perform(Task.java:348)
at org.apache.tools.ant.Target.execute(Target.java:357)
at org.apache.tools.ant.Target.performTasks(Target.java:385)
at org.apache.tools.ant.Project.executeSortedTargets(Project.java:1337)
at org.apache.tools.ant.Project.executeTarget(Project.java:1306)
at org.apache.tools.ant.helper.DefaultExecutor.executeTargets(DefaultExecutor.java:41)
at org.apache.tools.ant.Project.executeTargets(Project.java:1189)
at org.apache.tools.ant.Main.runBuild(Main.java:758)
at org.apache.tools.ant.Main.startAnt(Main.java:217)
at org.apache.tools.ant.Main.start(Main.java:179)
at org.apache.tools.ant.Main.main(Main.java:268)
Caused by: Error starting wsimport:
at com.sun.tools.ws.ant.WsImport2.execute(WsImport2.java:757)
at weblogic.wsee.tools.clientgen.jaxws.ClientGenImpl.execute(ClientGenImpl.java:169)
... 19 more
Caused by: com.sun.tools.ws.wscompile.AbortException
at com.sun.tools.ws.processor.modeler.wsdl.JAXBModelBuilder.bind(JAXBModelBuilder.java:136)
at com.sun.tools.ws.processor.modeler.wsdl.WSDLModeler.buildJAXBModel(WSDLModeler.java:2255)
at com.sun.tools.ws.processor.modeler.wsdl.WSDLModeler.internalBuildModel(WSDLModeler.java:194)
at com.sun.tools.ws.processor.modeler.wsdl.WSDLModeler.buildModel(WSDLModeler.java:140)
at com.sun.tools.ws.wscompile.WsimportTool.buildWsdlModel(WsimportTool.java:261)
at com.sun.tools.ws.wscompile.WsimportTool.run(WsimportTool.java:203)
at com.sun.tools.ws.wscompile.WsimportTool.run(WsimportTool.java:188)
at com.sun.tools.ws.ant.WsImport2.execute(WsImport2.java:738)
... 20 more

One thing you can try is running out of Jdeveloper, Set Weblogic Environment by %WL_home%\wlserver_10.3\server\bin\setWLSEnv.cmd and try running your ant task if you not see any error there might some issue with class-path setting in jdev

This might require more debugging I would suggest you to open SR with WLS WebService team with providing complete Test case to debug further.